Polymerization of ethylenically unsaturated monomers employing catalyst of aliphatic α-(hydroperoxy)azo compounds and salts thereof

ABSTRACT

New aliphatic azo compounds containing an α-hydroperoxy group and the alkali metal and alkaline earth metal salts thereof as represented by the general structure ##STR1## processes for preparing I where M is H and R is t-aliphatic by reacting t-aliphatic azo compounds having an α-halo substituent with about an equimolar amount of sodium or hydrogen peroxide; processes for converting I where M is H to its alkali or alkaline earth metal salt by reaction with aqueous solutions of the corresponding base or with calcium or sodium hydride; and the use of these novel compounds as polymerization initiators for vinyl monomers and as curing agents for resins. For example, 2-t-butylazo-2-hydroperoxy-4-methylpentane is prepared from sodium peroxide and 2-t-butylazo-2-chloro-4-methylpentane and used to polymerize vinyl chloride and to cure unsaturated polyester resin.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a division, of application Ser. No. 453,445, filed Mar. 21, 1974(now U.S. Pat. No. 4,010,152). Which is a continuation-in-part ofcopending application Ser. No. 88,249 filed Nov. 9, 1970, (nowabandoned) which in turn is a continuation-in-part of Ser. No. 725,180filed Apr. 29, 1968 (now abandoned), which in turn is acontinuation-in-part of application Ser. No. 616,158, filed Feb. 15,1967 (now abandoned), which is a continuation-in-part of applicationSer. No. 409,306, filed Nov. 5, 1964 (now abandoned).

BACKGROUND OF THE INVENTION

This disclosure relates to novel alkyl, cycloalkyl and aralkyl azocompounds containing an α-hydroperoxy group, and the alkali metal oralkaline earth metal salts thereof; to processes for their preparations;and to their use as polymerization initiators for ethylenicallyunsaturated monomers and as curing agents for polyester resincompositions.

To the best of applicants' knowledge, there are no known examples ofaliphatic-azo compounds as defined by structure I. Aromatic-azoalkanescontaining α-hydroperoxy groups are reported in R. Criegee and G.Lohaus, Chem. Ber. 84, 219 (1951); and in F. Minisci, Gazz. Chim. ital.89, 626 (1959). K. H. Pausacker, J. Chem. Soc., 3478 (1950); A. J.Bellamy and R. D. Guthrie, J. Chem. Soc. 2788 (1965); G. J. Karabatsoset al., J.A.C.S., 85, 3627 (1963); and H. C. Yas et al., J. Org. Chem.30, 2832 (1965) have studied auto-oxidation of arylhydrazones.

U.S. Pat. No. 3,278,304 describes a process for photopolymerization ofethylenically unsaturated organic compositions, using azo-hydroperoxidesas initiators. While only aromatic azo-hydroperoxides (derived fromaromatic hyrdazone) are used in the working examples, they state thataliphatic azo-hydroperoxides are suitable and that "all theseazohydroperoxides are manufactured according to known methods."Applicants, however, do not know of the previous existence of any suchaliphatic azohydroperoxides or of any known method for theirpreparation. Since aromatic azo compounds are normally much more stablethan the corresponding aliphatic azo compounds which are highlysusceptible to decomposition, it is submitted that the subject patentdoes not give sufficient information to suggest how such compounds mightbe prepared.

BRIEF SUMMARY OF THE INVENTION

This invention relates to

A. New aliphatic azo-hydroperoxides containing an α-hydroperoxy groupand the alkali metal and alkaline earth metal salts thereof: ##STR2##where: M is hydrogen, alkali metal (e.g. sodium, potassium, lithium) oralkaline earth metal (e.g. calcium, barium, magnesium);

m is the valence of M;

R is a C₁ to C₁₂ alkyl, C₃ to C₁₂ cyclo-, bicyclo- or tricycloalkyl, orC₇ to C₉ aralkyl radical;

R₁ and R₂ are separately selected from hydrogen and a C₁ to C₈ alkyl, C₃to C₁₂ cyclo-, bicyclo- or tricycloalkyl, C₇ C₁₂ aralkyl, C₆ to C₁₄ arylor 5 to 6 membered heterocyclic radical wherein the hetero atom is O, Sor N (i.e., as in furan, pyran, pyridine, pyrrole, thiophan or thiophen)or, taken together, R₁ and R₂ can form a C₃ to C₇ alkylene diradical(i.e., together with their common carbon atom, they form C₄ -C₈cycloalkyl); and one or more of each of R, R₁ and R₂ can be subsitutedwith lower (i.e., about 1-4 carbons) alkoxy, hydroxy, carboxy, loweralkoxycarbonyl, lower acyloxy (i.e., lower alkylcarbonyloxy), halogen(i.e., chlorine, bromine, fluorine, or iodine), cyano amido (as indimethylamido) or lower alkylsulfonato radicals;

B. A method for preparing ##STR3## by reacting about equimolar amountsof a tertiary-aliphatic α-halo-azo-compound, ##STR4## and sodiumperoxide (or hydrogen peroxide in the presence of an acid acceptor),where R₁ and R₂ are as defined above. X is chlorine or bromine and R' isthe same as R above where R is a C₄ to C₁₂ t-aliphatic (alkyl,cycloalkyl or aralkyl) radical (i.e., the R carbon attached to the azogroup must be a tertiary carbon);

C. A process for preparing I where M is alkali metal or alkaline earthmetal by contacting I where M is H (i) with at least an equivalent molaramount (preferably equivalent or slight excess) of a cold (preferably 0°to 15° C.) aqueous solution of the corresponding inorganic base, or (ii)with about an equivalent molar amount of sodium or calcium hydride;

D. The use of I as a polymerization initiator (free radical generator)for homo- or copolymerization of ethylenically unsaturated monomerswhich are responsive at suitable temperatures to free radicalgenerators, especially for initiating vinyl chloride polymerizations inthe 10°-60° C. temperature range; and

E. The use of I as a curing agent (free radical initiator) for thecuring of unsaturated polyester resin compositions in the presence ofthe novel I compounds, especially for curing unsaturated polyester-vinylmonomer blends at temperatures of 20°-90° C., preferably near roomtemperatures.

DETAILED DESCRIPTION OF INVENTION

In addition to the compounds (I) and methods set forth herein, othercompounds and preparatory methods are described in our application Ser.No. 725,180, filed Apr. 29, 1968.

Preparation of II

The above-described reaction of tertiary-aliphatic α-halo-azo compounds(III) with sodium (Or hydrogen) peroxide is run in inert solvents suchas ether, tetrahydrofuran, water, alcohols (above C₃), aqueous alcoholsand formamides). When alcohols are used as solvent, the C₁ - C₃ alcoholsshould not be used since they react with the α-haloazo (III) to formalkoxy derivatives. The reaction can be run at 0°-50° C., but preferablyis run at 10°-25° C. to obtain a practical reaction rate and a minimumof decomposition. The α-haloazo compound should be added slowly to theperoxide solution to prevent formation of the symmetrical peroxide whichoccurs when the α-haloazo compound is present in greater than a 1:1molar ratio to the peroxide. III can be added heat (as is) or in asolution of an inert solvent such as ether, hydrocarbons, chlorinatedhydrocarbons or C₄ or higher alcohols.

Novel compounds I (including II) have low thermal stability, making themexcellent low temperature free radical initiators, but also making themvery hazardous if not properly refrigerated upon storage. Unlikenon-peroxidic azo compounds, compounds I are subject to induceddecomposition and are very sensitive to contamination by acids, metalions and reducing agents. In addition, some of these compounds (forexample, where R is t-butyl and R₁ and R₂ are methyl) are very sensitiveto shock in the pure form.

It is preferred to prepare the novel I compounds in hydrocarbon solventsat concentrations of around 30-70%. At these concentrations one stillhas a practical concentration of I in the solvent and has reduced thesafety hazards tremendously. Moreover the I compound is still generallysoluble in the solvent at the recommended storage temperature. As thestructure of the I compound varies, the solubility of the I compoundvaries and adjustment of the concentration is required in some cases tokeep the product in solution.

Preparation of Salts of I

When converting I where M is H to the corresponding metal salts bystirring with cold aqueous solutions of base, the hydroperoxide (I) ispreferably added to the aqueous basic solution slowly with stirring sothat the temperature can be easily controlled. While any of theinorganic bases such as sodium, potassium, lithium, magnesium, calciumor barium hydroxide can be used, sodium and potassium hydroxide arepreferred.

The sodium and calcium salts can also be easily prepared and isolated byreacting a hydrocarbon or ether solution of the hydroperoxide (I) withequivalent amounts of sodium or calcium hydride. After preparation ofthe salts, they can be separated from the hydrocarbon or ether solventby filtration and stored under refrigerated conditions.

Utility

These new compounds (I) are free radical generators, polymerizationinitiators for vinyl monomers, curing agents for polyester resins,initiators for free radical initiated chemical reactions, blowing agentsfor producing foamed polymers and plastics, selective oxidizing agentsand organic intermediates for a variety of reactions such as preparingother azo-peroxides, e.g. azo-peresters and generators of reactant freeradicals.

It has been observed that these new compositions are initiators for thepolymerization of copolymerization of unsaturated monomers such asalkenes, vinyl halides, vinyl esters, vinylidene halides and alkenylaromatics.

Illustrative polymerizable monomers are ethylene, vinyl chloride,vinylidene chloride, vinyl acetate, vinylpyridine, vinylpyrrolidone,vinylcarbazole, butadiene, isoprene, acrylonitrile, acrylic acid,acrylic acid esters, methacrylic acid, methacrylic acid esters, styrene,chlorostyrene, methylstyrenes and in the high pressure polymerization ofethylene.

It is a further advantage of these compounds that many of thesepolymerizations can be carried out at room temperature or below withoutneeding any activators or co-catalysts present. This is especially truein the case of vinyl chloride. In addition, these compounds are veryefficient polymerization initiators. Specific illustrations are given inthe working examples.

These compounds are also very efficient curing agents of polyesterresins, even at very low levels of catalyst concentration, at roomtemperature. The cured polyester resins are water-white or off-white incolor compared to the reddish-brown resin obtained with previouslydisclosed phenylazohydroperoxides. Specific illustrations of thisutility are given in the working examples as well as comparative dataobtained with phenylazohydroperoxides and other peroxides disclosed inthe art.

Unsaturated polyesters which are used as the one component of thepolyester resin compositions according to the present invention are, forinstance, polyesters as they are obtained by esterifying preferablyethylenically unsaturated di-or polycarboxylic acid or their anhydrides,such as maleic acid, fumaric acid, glutaconic acid, itaconic acid,mesaconic acid, eitraconic acid, allyl malonic acid, allyl succinicacid, and others, with saturated or unsaturated polyalcohols such asethylene glycol; diethylene glycol (2,2'-dihydroxy ethyl ether);triethylene glycol (ethylene glycol bis(2-hydroxy ethyl ether);propanediol-1,2; butanediol-1,3; 2,2-dimethyl propanediol-1,3; butene(2)-diol-1,1, glycerol, pentaerythritol, mannitol, and others. Mixturesof such acids and/or alcohols may also be used. The unsaturated di- orpolycarboxylic acids may be replaced, at least partly, by saturatedcarboxylic acids such as adipic acid, succinic acid, sebacic acid,hydrophthalic acid, and others and their anhydrides such as phthalicanhydride. The acids used as well as the alcohols employed may besubstituted by other substituents, preferably by halogen. Examples ofsuitable halogenated acids are, for instance, tetrachloro phthalic acid;1,4,5,6,7,7-hexachloro bicyclo (2,2,1) heptene (5)-2,3-dicarboxylicacid, and others, or their anhydrides.

The other component of the unsaturated polyester resin compositions areunsaturated monomers, preferably ethylenically unsaturated monomers suchas styrene, vinyl toluene, methyl methacrylate, diallyl phthalate,dibutyl fumarate, acrylonitrile, triallyl cyanurate, α-methyl styrene,divinyl benzene, methyl acrylate, diallyl maleate, n-butyl methacrylate,ethyl acrylate, and others, which are copolymerizable with saidpolyesters.

A preferred resin composition contains as the polyester component theesterification product of propylene glycol (a polyalcohol), maleicanhydride (anhydride of an unsaturated dicarboxylic acid) and phthalicanhydride (anhydride of an aromatic dicarboxylic acid) and as themonomer component styrene.

The novel I compounds evolve one mole of nitrogen gas per mole when theyare decomposed. In addition, other gases are evolved from the breakdownand/or disproportionation of the radicals formed. Thus, compounds I arealso useful in applications where copious quantities of gases aredesired, such as in producing foamed polymers,

Compounds

Many novel compounds of the present invention are taught in the examplesto follow. Additional compounds which can be prepared according to thisinvention include: ##STR5##

EXAMPLES

The following examples illustrate the invention but in no way limit thescope thereof.

EXAMPLE I

Preparation of 2-t-butylazo-2-hydroperoxy-4-methylpentane ##STR6##

To a stirred solution of 1.56g (20. moles) of sodium peroxide in 30 ml.of 75% aqueous methanol in a 50 ml. erlenmeyer flask immersed in a coldwater bath, was added 4.1g (.02 moles) of2-t-butylazo-2-chloro-4-methylpentane dropwise. After the addition wascomplete, the reaction mixture was stirred for an additional 45 minutesand poured into ice water containing .02 moles of H₂ SO₄. The productwas extracted with pentane and washed with cold solutions of ammoniumsulfate and sodium bicarbonate, washed with water, dried over anhydroussodium sulfate, filtered and the pentane stripped off under reducedpressure while the flask was immersed in an ice bath. The yield was 2.7grams (67% of theory) and the product began to decompose when allowed towarm to room temperature. The infrared spectrum showed thecharacteristic hydroperoxide absorption at 3300-3400 cm⁻¹.

EXAMPLE II

Preparation of 2-t-butylazo-2-hydroperoxy-4-methylpentane ##STR7##

A solution of 50 g of the t-butylhydrazone of methyl isobutyl ketone in50 grams of odorless mineral spirits was added to a 250 ml. jacketedreactor equipped with a mechanical stirrer, thermometer, condenser, afitted polyethylene gas inlet tube and a condenser. The solution waswarmed to 35° C by circulating warm water through the jacket and withrapid stirring the oxygen was slowly bubbled into the solution. Thereaction was monitored by following the disappearance of thet-butylhydrazone by gas chromatography. After the reaction wasapproximately half complete (1 hour), the temperature was lowered to 20°C and the remainder of the reaction was carried out at this temperature.When the gas chromatographic scan indicated the t-butylhydrazone wascompletely oxidized (another hour) the solution was cooled to 0° C bycirculating ice water through the jacket. The solution was then weighedinto a cold polyethylene bottle and stored at -30° C. The yield was105.3g or 96.5% of theory. The infrared spectrum of the product showedthe strong absorbance of the hydroperoxide group at 3300-3400 cm⁻¹ and atrace amount of ketone (a decomposition product).

A pure sample of 2-t-butylazo-2-hydroperoxy-4-methylpentane was obtainedby low temperature recrystallizations from purified pentane. The purecompound is a low melting solid (below 0° C) and is not shock sensitiveat 12 inches (duPont tester).

EXAMPLE III Curing an Unsaturated Polyester-Styrene Resin with2-t-Butylazo-2-hydroperoxy-4-methylpentane

An unsaturated polyester resin was made by reacting maleic anhydride(1.0 moles), phthalic anhydride (1.0 moles), and propylene glycol (2.2moles) until an acid number of 45-50 was obtained. To this was addedhydroquinone at a 0.013% concentration. Seven parts of this unsaturatedpolyester was diluted with 3 parts of monomeric styrene to obtain ahomogeneous blend having a viscosity of 13.08 poise and a specificgravity of 1.14.

To 20 grams of this blend was added 0.2 grams of a 30% solution of2-t-butylazo-2-hydroperoxy-4-methylpentane in dodecane and the mixturestirred up well with a wooden spatula. The internal temperature wasrecorded as a function of time and a peak exotherm of 295° F (146° C)was reached in 13.5 minutes indicating an excellent cure of theunsaturated polyester-styrene resin blend had occurred. The resultantcured material was very hard and was water white in color.

Without an initiator, no cure of this resin blend occured even aftermore than 30 minutes at 212° F (100° C). Likewise2-phenylazo-2-hydroperoxy-4-methylpentane (a compound where R in (I) isphenyl and not covered by this invention) did not cure the resin blendat room temperature. A 1 percent loading of a 33% solution of2-phenylazo-2-hydroperoxy-4-methylpentane did cure the resin blend to ahard resin in 1.7 minutes at 82° C. This indicates that thephenylazohydroperoxides are higher temperature curing agents. The curedresin had an unattractive brown color however.

EXAMPLE IV Polymerization of Vinyl Chloride with2-t-Butylazo-2-hydroperoxy-4-methylpentane

2-t-Butylazo-2-hydroperoxy-4-methylpentane was used as an initiator inthe polymerization of vinyl chloride using the well known bottlepolymerization technique at autogenous pressures. The formulation usedin evaluation is set out below:

    ______________________________________                                        Vinyl chloride monomer    100g.                                               Water (distilled)         210ml.                                              *Methocel (1500 cps) (1% solution)                                                                      20ml.                                               Sorbitan monostearate (1% solution)                                                                     10ml.                                               Polyoxyethylene sorbitan monostearate                                                                   10ml.                                                (1% solution)                                                                2-t-Butylazo-2-hydroperoxy-4-methylpentane                                                              (variable)                                          ______________________________________                                         *A hydroxypropyl methylcellulose product of Dow Chemical                 

A water suspension was prepared as set out in the above formulation andadded to a 24 -ounce beverage bottle which was then frozen at -20° C. Aseries of bottles was prepared and varying amounts of the initiatoradded, followed by the freshly distilled vinyl chloride. The bottleswere capped, and placed in a water bath thermostatted at 30° C. The bathwas equipped to cause the rotation of the bottles end over end. Afterthe polymerization had continued at 30° C for 16 hours, the bottles werecooled, vented of excess vinyl chloride monomer and the yield ofpolyvinyl chloride determined gravimetrically. It was found that 0.053grams of 2-t-butylazo-2-hydroperoxy-4-methylpentane were required per100 grams of vinyl chloride monomer to obtain a 90% conversion topoly(vinyl chloride).

In contrast, 2-phenylazo-2-hydroperoxy-4-methylpentane (an art compound)gave a maximum conversion to poly(vinyl chloride) of only 7.0% atconcentration levels in the range of 0.026 to 0.189 grams per 100 gramsof vinyl chloride after 8 hours at 55° C. This compound was evaluated at55° C because its ten hour half-life is at ≈66° C whereas that of the2-t-butylazo-2-hydroperoxy-4-methyl-pentane used above is at 34° C.

For comparison, α,α'-azobis(isobutyronitrile) (a well known azocompound) which has a ten hour half life at 65° C gave a 90% conversionto poly(vinyl chloride) after 8 hours at 55° C using 0.127 grams per 100grams of vinyl chloride and2-(t-butylazo)-2-cyano-4-methyl-4-methoxypentane (disclosed in Ser. No.725,180) which has a 10 hour half life at 55° C gave a 90% conversion topoly(vinyl chloride) in 8 hours at 55°0 C using 0.051 grams per 100grams of vinyl chloride.

Thus, the novel I compounds of the present invention are very efficientinitiators for vinyl chloride polymerization while the analogous artcompounds (i.e., those where R = aryl in structure I) are veryineffective initiators for vinyl chloride.

EXAMPLE V

Preparation of 2-t-butylazo-2-hydroperoxypropane ##STR8##

A solution of 10 mls. of acetone t-butylhydrazone in 20 mls. of decanewas oxidized by passing dry air through the solution. The reaction wascarried out and followed using the same techniques used in Example II.The temperature was kept at 10°-20° C throughout the oxidation and thereaction required 6 hours to go to completion. The final product was notshock sensitive, however when the pure 2-t-butylazo-2-hydroperoxypropanewas isolated by low temperature recrystallizations it proved to be verysensitive to shock. The product was stored at -30° C.

A 50% solution of acrylonitrile in benzene was polymerized to a solid ina test tube by adding a couple of drops of the above decane solution toit at room temperature.

At a 1.0 weight percent loading the above decane solution cured theunsaturated polyester-styrene resin of Example III at room temperaturegiving a peak exotherm of 280° F (138° C) in 11.7 minutes and a veryhard cured resin which was water white in color.

In the polymerization of vinyl chloride (16 hours at 30° C) as inExample IV, it was found that 0.084 grams of2-t-butylazo-2-hydroperoxy-4-methylpentane were required per 100 gramsof vinyl chloride monomer to obtain a 90% conversion to polyvinylchloride.

EXAMPLE VI

Preparation of 2-t-Butylazo-2-hydroperoxyoctane ##STR9##

A solution of 10 mls. of the t-butylhydrazone of 2-octanone in 20 mls.of dodecane was oxidized by passing dry air through the solution. Thefirst half of the oxidation was carried out at 35° C for 1 hour (nooxidation occured at 20° C) and the second half carried out at 25° C for1 hour using the same techniques and apparatus described in Example II.The pure product was obtained by low temperature recrystallization frompurified pentane and was not sensitive to shock. The solution was storedat -30° C.

At a 1.0 weight percent loading the above dodecane solution cured theunsaturated polyester-styrene resin of Example III at room temperaturegiving a peak exotherm of 292° F (144° C) in 9.2 minutes and a very hardcured resin which was water white in color.

In the polymerizaton of vinyl chloride (16 hours at 40° C) using theprocedure described in Example IV, it was found that 0.025 grams of2t-butylazo-2-hydroperoxyoctane were required per 100 grams of vinylchloride monomer to obtain a 90% conversion to polyvinyl chloride.

EXAMPLE VII

Preparation of 2-t-Butylazo-2-hydroperoxy-4,4-dimethylpentane ##STR10##

A solution of 10 grams of the t-butylhydrazone of methyl neopentyl ketonin 20 grams of odorless mineral spirits was oxidized by passing oxygenthrough the solution. No oxidation occured at 20° C but the oxidationwas completely over in 1 hour at 25° C using the same technique andapparatus described in Example II. The solution was stored at -30° C.

At a 1.0 weight percent loading the above mineral spirit solution curedthe unsaturated polyester-styrene resin of Example III at roomtemperature giving a peak exotherm of 268° F (132° C) in 30 minutes anda very hard cured resin which was water white in color.

EXAMPLE VIII Preparation of 1-t-Butylazo-1-hydroperoxycyclohexane##STR11##

A solution of 80 grams of cyclohexanone t-butylhydrazone in 80 grams ofodorless mineral spirits was oxidized by passing oxygen through thesolution as in Example II. The solution was heated to 39° C to initiatethe oxidation. The reaction was followed by gas chromatography and afterthe oxidation was about 1/2 complete (1 hour) the temperature waslowered to 25° C and the remainder of the oxidation carried out at thistemperature (1/2 hour). After the cyclohexanone t-butylhydrazone hadcompletely reacted, the reaction was cooled to 0° C by circulating icewater through the jacket. The product was then weighed into a cold polybottle and stored at -30° C or below. The yield was 171 g (97.7% oftheory).

At a 0.67 weight percent loading the above mineral spirit solution curedthe unsaturated polyester-styrene resin of Example III at roomtemperature giving a peak exotherm of 315° F (157° C) in 7.0 minutes anda very hard cured resin which was water white in color.

In the polymerization of vinyl chloride (16 hours at 50° C) using theprocedure described in Example IV; it was found that 0.016 grams of1-t-butylazo-1-hydroperoxycyclohexane were required per 100 grams ofvinyl chloride monomer to obtain a 90% conversion to polyvinyl chloride.

1-Phenylazo-1-hydroperoxycyclohexane, an art compound, did not cure theunsaturated polyester-styrene resin of Example III to a hard resin atroom temperature but did cure the resin in 1.9 minutes at 82° Cindicating that the phenylazohydroperoxides are higher temperaturecuring agents. The cured resin was a dark reddish brown in color.

EXAMPLE IX Preparation of2-t-Butylazo-2-hydroperoxy-4-methoxy-4-methylpentane ##STR12##

A solution of 60 grams of the t-butylhydrazone of pentoxone(4-methoxy-4-methyl-pentanone-2) in 60 grams of odorless mineral spiritswas oxidized by passing oxygen through the solution as in Example II.The oxidation was initiated at 30° C by adding 2 drops of a 50% solutionof 2-t-butylazo-2-hydroperoxy-4-methylpentane. The oxidation was 1/2complete after 50 minutes at 30° C. The temperature was lowered to 20°C. and an additional 1 hour was required before the oxidation wascomplete. It was then cooled to 0° C. by circulating ice water throughthe jacket and weighed into a cold poly bottle and stored at -30° C. orbelow. The yield was 126 g (97% of theory). The solution is notsensitive to shock.

At a 1.0 weight percent loading the above solution cured the unsaturatedpolyester-styrene resin of Example III at room temperature giving a peakexotherm of 290° F. (143° C.) in 6.0 minutes and a very hard cured resinwhich was water white in color.

EXAMPLE X Preparation of 2-t-Cumylazo-2-hydroperoxyoctane ##STR13##

A solution of 4 grams of the t-cumylhydrazone of 2-octanone in 40 mls.of hexane was oxidized by passing oxygen through the solution as inExample II. The oxidation was initiated at 35° C. and the oxidationcarried out for 1 hour at 35° C. and then the temperature lowered to 25°C. for an additional hour. The reaction was followed by infraredspectroscopy. At the end of the reaction period the solution was cooledto 0° C., drained into a flask, placed on a rotating evaporator and thehexane stripped off at 0° C. The yield was 3.7g. It was immediatelydiluted to 50% with decane.

At a 2.0 weight percent loading, the above decane solution cured theunsaturated polyester-styrene resin of Example III at room temperaturegiving a peak exotherm of 254° F. (123° C) in 30 minutes and a very hardcured resin which was light straw yellow in color.

EXAMPLE XI Preparation of 2-t-Amylazo-2-hydroperoxy-4-methylpentane##STR14##

A solution of 9 grams of the t-amylhydrazone of methyl isobutyl ketonein 30 grams of purified hexane was oxidized by passing oxygen throughthe solution as in Example II. The oxidation was initiated at 38° C andthe oxidation carried out for 1 hour at 38° C. At the time the oxidationwas about 1/2 complete, the temperature was lowered to 25° C. Theoxidation was complete in 45 minutes, cooled to 0° C, drained into aflask, placed on a rotating evaporator and the hexane stripped off at 0°C until a 50% concentration was obtained. The solution was stored at-30° C.

EXAMPLE XII Preparation of 1-t-Butylazo-1-hydroperoxyheptane ##STR15##

A solution of 20 grams (0.109 moles) of the t-butylhydrazone of normalheptanal in 80 grams of odorless mineral spirits was oxidized by passingoxygen through the solution as in Example II. The oxidation wasinitiated at 37° C and the oxidation carried out for 40 minutes at 37° Cat which time the oxidation was complete. The temperature of thesolution was lowered to 0° C and the solution drained into a tared,cooled, polyethylene bottle, weighed and stored at -30° C. The solutionweighed 100.8 grams (88.5% yield).

At a 2.0 weight percent loading, the above solution cured theunsaturated polyester-styrene resin in Example III at room temperaturegiving a peak exotherm of 261° F (127° C) in 11.8 minutes and a veryhard cured resin which was a light straw yellow in color.

EXAMPLE XIII Preparation of 1-t-Butylazo-1-phenyl-1-hydroperoxy methane##STR16##

A solution of 20 grams (0.1135 moles) of the t-butylhydrazone ofbenzaldehyde in 80 grams of odorless mineral spirits was oxidized bypassing oxygen through the solution as in Example II. The oxidation wasinitiated at 35° C and the oxidation carried out for 15 minutes at 35°C. At this point gas chromatography indicated the oxidation wasapproximately half complete so the temperature was lowered to 25° C andthe oxidation continued for another 20 minutes at which time theoxidation was complete. The solution was cooled to 0° and drained into atared, cooled, polyethylene bottle, weighed and stored at -30° C. Thesolution weighed 100.2 grams (85.6% yield).

At a 5.0 weight percent loading, the above solution cured theunsaturated polyester-styrene resin of Example III at room temperaturegiving a peak exotherm of 195° F (90° C) in 23 minutes. The cured resinwas light yellow in color.

EXAMPLE XIV Preparation of 1-t-Butylazo-1-hydroperoxy-1-phenylethane##STR17##

A solution of 10 grams (0.0527 moles) of the t-butylhydrazone ofacetophenone in 40 grams of odorless mineral spirits was oxidized bypassing oxygen through the solution as in Example II. The oxidation wasinitiated at 35° C. The reaction was followed by gas chromatography,following the disappearance of the t-butylhydrazone peak. Thet-butylhydrazone peak immediately started to decrease so the temperaturewas lowered to 15°-20° C. The reaction was complete in 35 minutes. Thesolution was cooled to 0° and drained into a tared, cooled, polyethylenebottle, weighed and stored at -30° C. The solution weighed 50.0 grams(86% yield).

At a 2.5 weight percent loading, the above solution cured theunsaturated polyester-styrene resin of Example III at room temperaturegiving a peak exotherm of 257° F (125° C) in 4.3 minutes and a hardcured resin which was light yellow in color.

EXAMPLE XV Preparation of 2-Methylazo-2-hydroperoxy-4-methylpentane##STR18##

A solution of 20 grams (0.156 moles) of the methylhydrazone of methylisobutyl ketone in 80 grams of heptane was oxidized by passing oxygenthrough the solution as in Example II. The oxidation was initiated at37° C. The reaction was followed by gas chromatography, following thedisappearance of the methylhydrazone peak. The reaction was complete in20 minutes at 37° C. The solution was cooled to 0° C and drained into atared, cooled, polyethylene bottle, weighed and stored at -30° C. Thesolution weighed 103 grams (92.5% yield).

At a 2.0 weight percent loading, the above solution cured theunsaturated polyester-styrene resin of Example III at room temperaturegiving a peak exotherm of 315° F (157° C) in 6.5 minutes and a very hardcured resin which was water white in color.

In the polymerization of vinyl chloride (8 hours at 50° C) using theprocedure described in Example IV, it was found that 0.62 grams of2-methylazo-2-hydroperoxy-4-methylpentane were required per 100 grams ofvinyl chloride monomer to obtain a 90% conversion to polyvinyl chloride.

EXAMPLE XVI Preparation of 2-Cyclohexylazo-2-Hydroperoxypropane##STR19##

A solution of 5.0 grams (0.0324 moles) of acetone cyclohexylhydrazone in70 grams of heptane was oxidized by passing oxygen through the solutionas in Example II. The oxidation was initiated at 35° C. The reaction wasfollowed by gas chromatography, following the disappearance of thecyclohexylhydrazone peak. The reaction was complete in 35 minutes at 35°C. The solution was cooled to 0° and drained into a tared, cooled,polyethylene bottle, weighed and stored at -30° C. The solution weighed75.1 grams (85% yield).

At a 10.0 weight per cent loading, the above solution cured theunsaturated polyester-resin of Example III at room temperature giving apeak exotherm of 260° F. (127° C.) in 14.8 minutes and a hard curedresin which was water white in color.

In the polymerization of vinyl chloride (8 hours at 50° C.) using theprocedure described in Example IV, it was found that 0.0270 grams of2-cyclohexylazo-2-hydroperoxypropane were required per 100 grams ofvinyl chloride monomer to obtain a 90% conversion to polyvinyl chloride.

EXAMPLE XVII Preparation of Sodium 2-t-butylazo-isopropylhydroperoxide##STR20## Method A

To a slurry of 2.31 grams (0.055 moles) of 57% sodium hydride (inmineral oil) in 100 ml. of pentane in a 200 ml. 4 neck flask equippedwith a magnetic stirrer, thermometer, addition funnel and gas bubbler,was added 16.25 grams (0.055 moles) of a 54.5% pentane solution of2-t-butylazo-2-hydroperoxypropane dropwise and with rapid stirring. Thetemperature was held at 0°-5° C. during the addition and the2-t-butylazo-2-hydroperoxypropane solution was not allowed to warm upabove 10° C. during the addition. After the addition was complete, thereaction was stirred for an additional 40 minutes at 0° C. At this pointhydrogen evolution had ceased indicating the reaction was done. Attemptsto isolate the salt by filtration or by evaporation of the solvent underreduced pressure at 0° C. led to decomposition of the very unstablesalt.

Method B

To 22.0 grams (0.055 moles) of a 10% sodium hydroxide solution cooled to0° C. was added 16.25 grams (0.055 moles) of a 54.5% solution of2-t-butylazo-2-hydroperoxypropane dropwise and with rapid stirring overa 10 minute period. The temperature was held at 0° C. during theaddition and the 2-t-butylazo-2-hydroperoxypropane solution was notallowed to warm up above 10° C. during the addition. After the additionwas complete, the reaction was stirred for 2 hours at 0° to 5° C. Thesalt was a white solid. A 50 ml. portion of ice cold water was added todissolve the salt. The mixture was then extracted with pentane. Theaqueous solution of sodium 2-t-butylazo-isopropylhydroperoxide wasseparated and refrigerated at 5° C. The pentane layer was dried overanhydrous-sodium sulfate, filtered and the solvent evaporated at 0° C.under reduced pressure to leave 1.2 grams (13.6%) of unreacted2-t-butylazo-2-hydroperoxypropane.

The aqueous solution was then cooled to 0° C. and 60 ml. of pentane wasadded. The mixture was then acidified with dilute HCl to a pH of 4. Thepentane layer was separated and washed with H₂ O, dried over anhydroussodium sulfate, filtered and the solvent evaporated at 0° C. underreduced pressure to leave 6.4 grams (83.5% recovery) of2-t-butylazo-2-hydroperoxypropane.

EXAMPLE XVIII Preparation of Potassium2-t-butylazo-isopropylhydroperoxide ##STR21##

To 15.4 grams (0.0275 moles) of a 10% potassium hydroxide solutioncooled to 0° C. was added 8.12 grams (0.0275 moles) of a 54.5% solutionof 2-t-butylazo-2-hydroperoxypropane in pentane dropwise and with rapidstirring. The temperature was held at 0° C. during the addition and the2-t-butylazo-2-hydroperoxypropane solution was not allowed to warm upabove 10° C. during the addition. After the addition was complete, thereaction was stirred for 21/2 hours at 0° to 5° C. The aqueous mixturewas extracted with pentane. The aqueous solution of potassium2-t-butylazo-isopropylhydroperoxide was separated and refrigerated at 5°C. The pentane layer was dried over anhydrous sodium sulfate, filteredand the solvent evaporated at 0° C. under reduced pressure to leave 1.2grams (27.2%) of unreacted hydroperoxide. The aqueous solution wascooled in an ice bath and 50 ml. of pentane added. The mixture wasacidified to pH 4 with dilute HCl to convert the potassium salt back tothe free hydroperoxide. The pentane layer was separated and washed withwater, dried over anhydrous sodium sulfate, filtered and stripped. Theresidue weighed 3.0 grams indicating that 93% of the potassium salt wasrecovered.

EXAMPLE XIX Preparation of the Sodium Salt of2-t-Butylazo-2-hydroperoxy-4-methylpentane ##STR22##

To a slurry of 0.95 grams (0.0224 moles) of 57% sodium hydride (inmineral oil) in 50 ml. of pentane in a 100 ml. 4 neck flask equippedwith a magnetic stirrer, thermometer, addition funnel and gas bubbler,was added 9.0 grams (0.0224 moles) of a 50% solution of2-t-butylazo-2-hydroperoxy-4-methylpentane in odorless mineral spirits.The solution was added dropwise and with rapid stirring, holding thetemperature of the reaction mixture at 0°-5° C. and not allowing thetemperature of the azo-hydroperoxide solution in the dropping funnel torise above 10° C. After the addition was complete (15 minutes), thereaction was stirred for an additional 30 minutes at 0° to 5° C. At thispoint hydrogen evolution had ceased indicating the reaction wascomplete. The reaction mixture was filtered on a precooled filter andsucked dry on the filter. The filter cake was then transferred to abeaker cooled in dry ice. The salt almost immediately decomposed,evolving a white smoke.

EXAMPLE XX Preparation of the Sodium Salt of1-t-Butylazo-1-hydroperoxycyclohexane ##STR23##

To a slurry of 1.05 grams (0.025 moles) of 57% sodium hydride (inmineral oil) in 50 ml. of pentane in a 100 ml. 4 neck flask equippedwith a magnetic stirrer, thermometer, addition funnel and gas bubbler,was added 10.0 grams (0.025 moles) of a 50% solution of1-t-butylazo-1-hydroperoxycyclohexane in odorless mineral spirits. Thesolution was added dropwise and with rapid stirring, holding thetemperature of the reaction mixture at 0°-5° C. and not allowing thetemperature of the azo-hydroperoxide solution in the dropping funnel torise above 10° C. After the addition was complete (15 minutes), thereaction was stirred for an additional 30 minutes at 0° to 5° C. At thispoint hydrogen evolution had ceased indicating the reaction wascomplete. The reaction mixture was filtered on a precooled filter andsucked dry on the filter. The filter cake was then transferred to aprecooled, tared beaker and weighed. The salt weighed 5.0 grams (90%yield) and was stable at dry ice temperatures. The salt decomposes whenallowed to stand at room temperature. It is mildly shock sensitive(smokes at 10 inches on the duPont tester).

What is claimed is:
 1. In a process for the homo- or copolymerization ofethylenically unsaturated monomers which are responsive at suitabletemperatures to free radical generators as polymerization initiators,the improvement which comprises employing as the free radical generatora compound of the formula ##STR24## wherein: M is selected from thegroup consisting of hydrogen, alkali metal and alkaline earth metal;m isthe valence of M; R is selected from the group consisting of C₁ - C₁₂alkyl, C₃ - C₁₂ cyclo-, bicyclo- or tricycloalkyl, and C₇ - C₉ aralkyl;R₁ and R₂ are separately selected from the group consisting of hydrogen,C₁ - C₈ alkyl, C₃ - C₁₂ cyclo-, bicyclo- or tricycloalkyl, C₇ - C₁₂aralkyl, C₆ - C₁₄ aryl and 5 - 6 membered heterocyclic wherein thehetero atom is O, S or N, and R₁ and R₂ taken together form C₃ - C₇alkylene; and one or more of each of R, R₁ and R₂ can be substitutedwith a member selected from the group consisting of lower alkoxy,hydroxy, lower alkoxycarbonyl, lower acyloxy, halogen, cyano,dimethylamido and lower alkylsulfonato.
 2. claim 1 wherein the monomeris vinyl chloride.
 3. claim 2 wherein said generator is2-t-butylazo-2-hydroperoxy-4-methylpentane or its sodium salt.